Air blast circuit breaker with auxiliary enclosed housing



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H. FORWALD Filed March 2, 1965 Oct. 31, 1967 AIR BLAST CIRCUIT BREAKER WITH AUXILIARY ENCLOSED HOUSING United States Patent 3,350,529 AIR BLAST CIRCUIT BREAKER WITH AUX- ILIARY ENCLOSED HOUSING Haakon Forwald, Grottvagen 31, Ludvika, Sweden, assignor to Allrnanna Svenska Elektriska Aktiebolaget, Vasteras, Sweden, a corporation of Sweden Filed Mar. 2, 1965, Ser. No. 436,531 Claimspriority, application Sweden, Mar. 12, 1964, 3,065/64 1 Claim. (Cl. 200-148) ABSTRACT OF THE DISCLOSURE An air blast circuit breaker has inside a housing filled with compressed air an auxiliary enclosed housing with an opening opposite to an opening in the fixed contact. The movable contact passes through the opening in the auxiliary housing leaving an annular opening therebetween which permits a flow of cool air from the auxiliary housing after the blast valve is opened.

This invention relates to air blast circuit breakers, and more specifically relates to the provision of an auxiliary chamber within the main container of an air blast circuit breaker which auxiliary container is normally filled with compressed air, the auxiliary chamber providing a flow of relatively cool air toward the end of the interrupting operation.

Air blast circuit breakers are well known to the art, and commonly contain a main pair of cooperating contacts positioned within a container which is filled with compressed air. One of the contacts is generally a fixed contact which has an opening therethrough which communicates with a blast valve which, in turn, communicates with the external atmosphere. Thus, when the movable contact is moved to a disengaged position, the blast valve is opened 50 that a strong blast of compressed air flows through the opening in the movable contact and out of the chamber, thereby assisting in cooling and extinguishing the are.

In this operation, the arc is generally extinguished at zero current. At this time, however, the air flow through the arc and out of the chamber is somewhat diminished, and its temperature is very high since this air has been exposed to the hot arc. Therefore, the air passing through the open contacts at zero current may not have sufficient dielectric strength to prevent restrike, or to Withstand the .recovery voltage across the contacts.

The principle of the present invention is to provide an auxiliary chamber within the main container which has a small opening therein in communication with the area immediately adjacent the opening in the stationary contact. Therefore, during the main portion of the air blast cycle, relatively little air will be withdrawn from the auxiliary container and through the arc and out of the container, since there is a relatively equal pressure within the main body of the container and in the auxiliary chamber. However, toward the end of the air blast operation, and when zero current is reached, the pressure within the main body of the container will have decreased. Therefore, a relatively high rate of flow of air out of the auxiliary chamber will occur being that this air is relatively cool with respect to the remaining air in the body of the container, since it has not been directly exposed to the arc. Thus, toward the end of the cycle, an additional supply of cool air is provided which passes through the arcing area, thus increasing the dielectric strength of the air between the separated contacts and improving the probability that the separated contacts will successfully withstand the recovery voltage across the contacts.

Accordingly, a primary object of this invention is to improve the interrupting capability of an air blast circuit breaker.

Another object of this invention is to provide an auxiliary source of cool air for passage through the arcing area of an air blast circuit breaker toward the end of the interruption operation.

Yet another object of this invention is to provide a relatively cool air flow through the open contacts of an air blast circuit breaker toward the end of the interruption operation.

These and other objects of this invention will become apparent from the following description when taken in connection with the accompanying drawing which shows a partial cross-sectional view of a typical interrupter of a high voltage air blast circuit breaker constructed in accordance with the present invention.

Referring now to the drawing, the interrupter structure is comprised of a main container or housing which includes an insulation cylinder 10 which has conductive end caps 11 and 12 secured to the opposite ends thereof in an air-tight manner.

A conduit 13 passes through the end cap 11 to provide high pressure air to the interior of the container. The bottom of the container carries a stationary contact structure 14 which has a flange 15 sealed across an opening 16 in the end cap 12.

As schematically illustrated in the drawing, the stationary contact 14 is associated with a blast valve 17 which is operable to connect the interior space 18 of the stationary contact 14 to the external atmosphere in the usual manner.

The upper end of stationary contact 14 is provided with a nozzle opening 19 which is in communication with the interior of the main container. A movable contact 20 which is comprised of a contact rod 21 and an arcing contact tip 22 moves through an opening in end wall 11 and is in sealed relationship with respect thereto by virtue of suitable gaskets such as gasket 23.

The movable contact 20 is shown in its disconnected position with respect to stationary contact 14. Clearly, the rod 21 is movable downwardly so that the contact can seat on top of and within the walls of orifice 19.

The stationary contact 14 is further provided with an arcing contact 24 so that the are between the movable contact 20 and stationary contact 14 will strike from the arcing tip 22 to the arcing contact section 24, as illustrated.

In accordance with the invention, an auxiliary closed chamber 25 is secured to the end cap 11 in a substantially air-tight manner as by brazing or any other suitable operation. The lower end of chamber 25 has an opening 26 therein which is relatively closely fitted about the end of movable contact 20. That is to say, a small annular gap 27 is defined between the outer area of the lower portion of movable contact 20 and the opening 26. Container 25 is substantially sealed except for this annular opening 27.

The annular opening 27 is arranged to have a relatively small area with respect to the relatively large area opening of orifice 19. The opening 27 is further arranged to have a relatively small area with respect to the effective area with which the opening 19 communicates with the rest of the container. That is to say, an annular inlet area is defined between the top of stationary contact 14 and the bottom of auxiliary container 25 which permits gas to flow from the remote regions of the container and toward the nozzle or orifice 19. The opening 27 is specifically made to be relatively small with respect to this latter mentioned inlet area for nozzle 19. It should also be noted that this opening 27 is purposely provided in relatively close proximity with respect to nozzle 19.

In operation, and assuming that the contacts 20 and 14 are in their closed position, the blast valve 17 is opened simultaneously with the movement of the contact rod 21 toward the upper position shown. An arc is then struck between arcing contact sections 22 and 24, and simultaneously therewith a strong blast of compressed air, illustrated by arrows 28 and 29, flows from the main regions of the container through the nozzle 19, thereby to cool the arc and aid in its extinction.

During this time, since the effective area 27 is so small, the compressed air within the chamber 25 will experience relatively little flow, indicated by arrows 30 and 31. Toward the end of the interrupting cycle, however, the pressure within the main portion of the container will have decreased, while the temperature of the remaining air within the main container will be substantially increased by virtue of its direct exposure to the arc. The air within the auxiliary container 25, however, remains cool with relation to the remaining air within the main portions of the container, since it is not directly exposed to the arc. Therefore, toward the end of the interrupting cycle, and when the pressure within the main body of the container has decreased, the relatively high pressure air still remaining within auxiliary container 25 will now be sucked toward the arc and through the nozzle or orifice 19. That is to say, when the arc current approaches zero, the speed of the air through the nozzle 19 increases, while its static pressure decreases. This, in connection with the general pressure decrease in the container, creates a pressure differential between the interior of container 25 and the air pressure external of container 25, thereby producing an increased quantity of cool air flowing through orifice 27 and toward orifice 19, thereby cooling down the hot air flowing through nozzle 19.

Therefore, the relatively cool air from the auxiliary container 25 will mix with the heated air from the remaining portions of the container so that a relatively cooler flow of air will pass through nozzle 19 toward the end of the interrupting cycle, whereupon the dielectric strengthof the air at that time is increased. Therefore, when zero current is reached, there is less likelihood of a restrike between the cooperating contacts due to the recovery voltage across the contacts.

Although this invention has been described with respect to its preferred embodiments, it should be understood that many variations and modifications will now be obvious to those skilled in the art, and it is preferred, therefore, that the scope of the invention be limited not by the specific disclosure herein, but only by the appended claim.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

An air blast circuit breaker comprising a housing filled with compressed air, a stationary contact, a movable contact movable into and out of engagement with said stationary contact, an opening in said stationary contact, a blast valve connected between said opening in said stationary contact and the atmosphere external of said housing,

and an auxiliary enclosed housing within said housing;

said auxiliary enclosed housing and said movable contact defining between them an annular opening; said annular opening being in close proximity to said opening in said stationary contact; said annular opening having a relatively small area in comparison to the area of said opening in said stationary contact whereby initial air flow through said opening in said stationary contact is mainly comprised of the air in said housing exterior of said auxiliary housing followed by a flow of cool air from said auxiliary housing.

References Cited UNITED STATES PATENTS 2,494,661 1/195O Latour 200-148 3,185,802 5/1965 Amalric 200-l48 ROBERT S. MACON, Primary Examiner. 

